Dropout fuse construction having a combined upper latch and contact



April 13, 1965 F. E. REIBER ETAL 3,178,536

DROPOUT FUSE CONSTRUCTION HAVING A COMBINED U R LATCH AND CONTACT 'ledApril 17, 1961 United States Patent O 3,178,536 DRPUT FUSE CNSTRUCTIONHAVING A COMBINED UPPER LATCH AND CONTACT Frederick E. Reiber and GeneL. Miller, Bloomington,

and Robert .1. Lawrence, Ellettsville, Ind., assignors to WestinghouseElectric Corporation, East Pittsburgh,

Pa., a corporation of Pennsylvania Filed Apr. 17, 1961, Ser. No. 103,634Claims. (Cl. 200-114) This invention relates, in general, to electriccircuit interrupters of the dropout fuse type, and more specifically, tothe contact mechanism therein.

In the past, the fixed contact of a fuse cutout of one type has requiredthe presence of a separate latch mechanism for engaging the fuse holderContact to maintain the contact in engagement with the fixed contactduring normal circuit operation, as in copending application Serial No.91,219, tiled February 23, 1961, by A, I. Fink et al., which issued lune23, 1964, as US. Patent No. 3,138,681. In other prior devices where thecontacts are of the gripping finger type, the need for a separate latchis eliminated, but a separate spring mechanism is required to bias thefuse tube holder and contact in the dropout direction to effect adisengagement between the fuse holder contact and the fingers of theiixed contact, as for example in Patent No. 2,938,693.

It is an object of this invention to provide a fixed contact mechanismfor a dropout fuse cutout, which contact eliminates the necessity of aseparate latch means and also eliminates the necessity for separatebiasing means for the fuse tube.

More specically, it is an object of this invention to shape the fingersof a fixed contact device for a fuse cutout in a unique manner toprovide for latching the fuse holder contact between the lingers duringnormal circuit operation and to also provide for biasing the fuse holdertoward the dropout position.

Further objects and advantages will readily become apparent to thoseskilled in the art upon reading the following speciiication, takenrinconjunction with the drawings, in which:

FIGURE l illustrates a -generally vertical sectional view taken throughan enclosed fuse cutout, the contacts of the present invention beingshown in side elevational view, and the fuse cutout being illustrated inits operative condition for carrying line current therethrough;

FIG. 2'is an enlarged top plan View of the fixed contacts shown in FIG.l and embodying this invention; and

FIG. 3 is an enlarged side elevational View of the contact backer springfor the contacts of FIG. 2.

Referring to the drawings, there is shown a fuse cutout generallyindicated by the reference numeral 1 and which is substantiallyidentical to the' fuse cutout disclosed in the copending applicationSerial No. 91,219, filed February 23, 1961, now Patent No. 3,138,681,with exceptions hereinafter described as constituting the presentinvention.

The fuse cutout 1 includes an insulating housing 2, which may be formedof any desired insulating material, such as porcelain.

The porcelain housing or box 2 comprises a rear wall 3, a top wall 4,and oppositely disposed side walls 5 (only one shown). 1t will be noted,therefore, that the front and bottom of the porcelain box 2 are open.The rear wall 3 is provided with an inwardly extending protuberance 7forming with an integral flange 8 a transverse baille intermediate theends of the insulating casing 2. The protuberance 7, as shown, isprovided with a cavity 11 opening to the outer side of rear wall 3 andadapted to receive one end of a mounting bracket 12 for supporting thecasing 2, for example, from a cross-arm hanger.

' tact 151i and the fuse element 33.

31,173,536 Patented Apr'. 13, 1965 ice As shown in FIG. 1, the mountingbracket 12 may be apertured, as at 15, to provide better securementwithin a resilient cement 16 contained within the cavity 11 and may beof a type described in the hereinbefore mentioned copendiny application.The cavity 11 may also be sanded during fabrication of the fuse casing 2for additional strength of securement.

Within insulating casing 2 there is provided upper and lower contactassemblies 17 and 18, respectively, secured within cavities 21, 22,respectively, provided in the inner surface of rear wall 3 of the casing2. The upper contact assembly 17 includes a forwardly projectingU-shaped contact strip (FIG. 2) of any desired conducting material,such, for example, as copper or the like, with a resilient U-shapedbacking strip 151. Preferably, the backing `strip 151 is formed from asuitable resilient material, such -as Phosphor bronze.

The U-shaped contact strip 156 comprises a bight portion or base 152,having integrally fixed at the ends thereof a pair of leg members 153extending outwardly in laterally opposed relationship wi-th respect toeach other. Each of the leg members 153 is doubly recurved along itslength resulting in two spaced points 154 and 155 on each leg, whichpoints are bent inwardly toward each other to comprise an inner stop154, 154 and an outer stop 155, 155, respectively. The inner stopinhibits inward movement of the upper end of fuse element 33 while theouter stop inhibits outward movement of the fuse element 33 after theelement has been moved inwardly of the outer stop. The intermediateportions 156 of each leg, between the points 154 and 155 is curved awayfrom the other so as to congruently mate with opposite sides of theupper end of the previously described fuse element 33, thu-s providingsufficient electrical connection `between the con- As best seen in FIG.2, the intermediate portions 156 are canted with respect to the verticalplane of the strip 152 so as to are laterally outwardly and downwardly.

The outer end portions 157 of the leg members 153 are bent laterallyaway from each other to serve as a guide for the inwardly moving upperend of fuse element 33.

The hacker 151 is comprised of a bight portion 15S and integral legportions 159 shaped to congruently mate with legs 153 of contact 150 toprovide resiliency to the contact. lf the contacts are constructed lofmaterial having sufficient inherent resiliency, the hacker may bedispensed with.

The foregoing structural characteristics of the contacts 151i provideseveral advantages. The basic U-shape of the contact 15() providesiirmer contact during passage of current which provides magnetic fluxholding the Contact legs 153 together to minimize burning. The recurvednature of the legs 153 provide integral latch means for holding the fuseelement 33 securely in place during normal operation, thus eliminatingseparate latch means. The canted or flared nature of the intermediateportion 156 of legs 153 redirect the previously described holding forceto a resultant downward force against the fuse element 33 and axially oftie fuse element to urge the hereinbefore described toggle mechanism tothe toggle release position upon fusing of the fuse link to effect rapidopening of the fuse cutout in the manner hereinafter described indetail.

The lower contact assembly 18 includes a U-shaped contact strip 31 and aresilient U-shaped backing strip 32, the latter being formed from aresilient metallic material, such as phosphorus bronze. The intermediateportions of the contact legs converge and the end portions diverge toform a sloped surface suitable for engaging and stopping the movablecontacts as fully described in detail in the copending applicationpreviously mentioned. The contact hacker 32 is curved to respectivelymate with the intermediate and outer portions of the contact strip 31.

The support terminal 38 is suitably apertured for receiving studs 43anchoring the stationary contacts 151) and backer 151 to the end ofsupport 38.

The contact and backing strips of both the contact assemblies 17, 13 aremounted in position by means of an angle-shaped support bracket 40, apair of rivets 41 being employed for the connection.

lt will be observed that contact strip 150 has a downwardly extendingend portion 44 which is disposed within box-shaped support terminal 33.Lower contact strip 31 likewise has a depending portion 4S, which issimilarly positioned. A pair of terminal screws 46 are threaded of eachsupport terminal 38 and have contacting shoe clamps 48 rotatably securedthereto at the inner ends thereof.

As a result of the foregoing construction, the line conductor and alsothe load conductor, not shown, may be threaded into the side leadopening (not shown) of casing 2 and forced under pressure by thecontacting shoe clamps 48 directly against the curved dependingreceptive portions 44, 45 of contact strips 150, 31, respectively. As aresult, no unnecessary joints are provided in the current path extendingthrough the fuse cutout 1.

It will be noted that the angled support brackets 40 have an angledportion 50, which is cemented into the cavities 21, 22 of the casing 2.Any suitable cement, such as high-strength mineralead cement 51, may beemployed.

With reference to FIG. l, it will be noted that the porcelain fusehousing 2 is provided with threaded metallic pivot pins 53 extendingthrough opposite sides of the housing 2 and retained by cooperatinginsulating nuts (not shown). The pins 53 (only one shown) form inwardlyextending trunnions to removably pivotally support a fuse-holder door,generally designated by the reference numeral 57.

Preferably the fuse-holder door 57 is formed of a suitable insulatingmaterial, such, for example, as porcelain, a synthetic resin, or thelike. The molded door 57 is provided with an apertured handle 58, whichmay be manipulated by a switchstiek at a distance, or by hand for thelower voltages. The openings 59 in the handle 58 may be grasped by thehand of the lineman, but preferably, for reasons of safety, switchstickoperation is desirable with the prong of the switchstick inserted withinthe opening 59 to effect closing and opening rotative motion of thefuse-holder door 57 about the pivot pins 5.3, as hereinafter more fullydescribed.

Fuse-holder door 57 comprises a door panel 60 having a rearwardlyintegral apertured mounting projection 61. In addition, door 57 has anintermediately disposed recess 63 for the accommodation of a spongerubber, washershaped barrier member 64, and rivets 65 molded with thedoor. Also fuse-holder door 57 has a transverse integral tlange 66 withan arcuate cutout portion, not shown, for accommodating a tubularfuse-holder, generally designated by the reference numeral 68. The lowerportion of `the molded door 57 is provided with a pair of trunnionreceiving llared notches 71 (only one shown) for receiving the pivotpins 53 on casing 2. The top of the door 57 is provided with a topinwardly extending flange portion 73.

The tubular fuse-holder 68 comprises a top knurled contact cap 74, whichis threaded into a fuse ferrule 75, the latter, in turn, being threadedupon the upper threaded end of a fuse tube 76 and iixedly cementedthereto.

It will be noted that the contact cap nut 74 of fusible device 33 istapered from the base inwardly toward the top to fit in mating relationwith the previously described dared intermediate portions 156 ofcontacts 150. In addition, the cap has a cylindrical recess (not shown),which is not utilized in this invention but engaged by the latchingportion of a spring latch shown in copending application Serial No.`91,219.

The mounting aperture 78 of mounting projection 61 has a shoulderportion 81, which limits the downward movement of fuse ferrule 75 whentubular fuse holder 63 is inserted into mounting aperture 78.

As well known by those skilled in the art, a button-type fuse-linkassembly, generally designated by the reference numeral 82, is insertedinto the top of tubular fuse-holder 63 following removal of knurledContact cap 74. The buttonhead of the link assembly is clamped betweenthe bottom of the contact cap 74 and a threaded plug, not shown,threaded interiorly within fuse ferrule 75. The fuse link may be of thetype described in United States Patent 2,343,723, issued March 7, 1944,to James M.. Wallace and assigned to the same assignee as the presentapplication.

The lower cable or tail 83 of the fuse-link assembly 82 extends throughthe lower open end of the bore provided within fuse tube 76 and isclamped between a freely rotatable washer 84 of a terminal clamp 85 andthe knurled side (not shown) of a pivotally mounted support link, ordoor hinge 87. In the intact, or unblown condition of the fuse link 82,a toggle means S8 is maintained in its set or unbroken position.However, when fuse link 82 fuses upon overload or fault-currentconditions, the cable 83 is released, and the toggle means 38 breaks, orcollapses, to permit lowering and outward movement of the fuse-holderdoor 57 and consequent unlatching of contact cap 74 from the aredportions 156 of contacts 150. The entire fuse-holder door 57 then dropsdownwardly to the dropout indicating position shown by dot-dash lines inFIG. 1.

Preferably, the fuse tube 76 is composite in construction having aninner gas-evolving liner of fiber, or like material, and an outersurrounding casing of insulating material preferably glass reinforcedepoxy. By using a strong outer layer, greater bursting strength isachieved and a thinner outer wall is permitted, thus allowing a thickerlayer of ber. The thicker ber provides a greater ability to withstanderosion due to arcing. The evolution of the gas from the iber linerduring the drawing of the arc within the fuse-tube bore will assist anare extinction, the evolved gas being expelled downwardly through thelower open end of the fuse tube 76 with expulsive action. This expulsiveaction will, of course, assist in the ejection of the lower remnant ofthe fuse link out of the fuse tube.

It will be noted that the rivets 65, molded with the door 57, areemployed to secure xedly in place a latch `bracket or catch 93. Therivets 65 extend through appropriately positioned holes of latch bracket93 and have their inner ends swaged, or peened over to rigidly mount thelatch bracket 93 on the door 57. Preferably, a resilient rubber Vpad 95of generally rectangular configuration is disposed between the innerside of the door panel 60 at the bottom of a recess 96, and the bightportion of latch bracket 93 for minimizing shock imposed upon the moldeddoor 57 during operation of the cutout. The pad 95 is, of course,provided with apertures to accommodate the pair of rivets 65.

The legs 98 of latch bracket 93 have three threaded holes provided inthe sides 98 of the latch bracket 93. The upper two holes receive theinner ends of pivot screws 102 (FIG. 1), the shank portions of whichpass with clearance through suitable pivot holes of supporting link S7.The inner extremities of the two pivot screws 102 extend into boredopenings, or recesses provided in the side walls of fuse tube 76. Theserecesses, not shown, do not, however, extend to the inner surface of thebore extending through fuse tube 76. Thus, the inner ends of the pivotscrews 102 serve to iixedly attach the fuse-holder 68, including thefuse tube 76, to the door 57. By unscrewing the pivot screws 102,however, the supporting link 87 may readily be removed from the latchbracket 93, or door 57, and the freed fuse tube 76 may be removed fromdoor 57 by upward withdrawal movement through mounting aperture 78 ofprojection 61. When desired, a new fuse tube 76 may be substituted inthis manner for an old fuse tube 76.

The toggle means 83 comprises the fuse-holder 63 as one leg of thetoggle, and the supporting link 87 as the other leg of the toggle. Thesupporting link S7 is received upon the pivot pins 53 supported upon theside walls 5 and 6 of the casing 2. The link S7 may be readily attachedand detached with respect to supporting pivots 53 by movement of thelink 87 to cause entrance or exit of supporting pins 53 into slots inthe supporting link 37 which slots line up with the notches 71 providedin opposite side edges of ydoor panel 60 to permit the link 37, whenassembled with the fuse holder 63 and door S7, to -be engaged ordisengaged with pivot pins 53. The notches 71 in the door panel 60 are,as shown, flared outwardly to facilitate easy entrance of pivot pins 53into the notches 71 and slots in the supporting link 87.

The lower threaded hole or link 87 accommodates a converting screw 166,which passes with clearance through a hole in link S7, and therebyadapts the fuse cutout 1 for non-dropout operation. Removal of thisconverting screw 106, which is mounted in place at the factory, providesdropout operation, since the toggle means 88 is then free to collapse.lf the converting screw 106 is maintained in position, as supplied fromthe factory, the supporting link S7 is rigid with latch bracket 93 anddoor S7, and the toggle means 8S is rendered inoperable.

It will be .noted that a spring latch, generally designated by thereference numeral 16S, is mounted at the lower end of the supportinglink 87 and includes a sleeve `169. This spring latch 103 described indetail in copending application Serial No. 91,219 is mounted upon thedoor-hinge assembly, and permits only a correct and controlled forceupon the fuse link and aids the fuse cutout 1 in clearing faults. Italso serves as a fuse-link flipper indicating a blown fuse when the fusecutout 1 is adjusted for non-dropout operation.

1t will be noted that supporting link 87 has a contacting portion 116for accommodating the fuse tube 76 in the closed-circuit position of thedevice, as shown in FlG. l. The contacting portion 116 has flared ends114 for mating engagement with outer end portions of the lower contactstrip 31 of lower Contact assembly 18 with a wiping and pressuralengagement. The upper contact cap nut 74 likewise engages the contactplate legs 153 with pressural engagement. Thus, adequate contactpressure is provided in the latched closed position of the fusibledevice 1. This contact pressure tends to cause breaking or collapse ofthe toggle means S8, which is resisted by the fuse-link assemblymaintaining the spring latch in its locking position, as shown in FIG.l. The contact pressure provided between the resilient U-shaped lowercontacts 31 and the movable contacts 116 on support link 87 in adirection perpendicular to the fuse tube serves to provide a forceurging the fuse tube 68 and support link 87 outwardly of the box 2 toassist in collapsing the previously described toggle mechanism when thefuse link S3 fuses.

When the line conditions are such as to permit excessive current to flowthrough the cutout 1 by way of contact assemblies 17, 1S and fuse-linkassembly 82, this excessive current will cause fusing of the fusibleelement disposed within fuse tube 76 and associated with fuselinkassembly 82. The fusing the fusible element will release thespring-biased latching device 108 causing it to operate to effectwithdrawal of the lower remnant of fuse-link assembly 82 downwardly outof the lower open end of the fuse tube 76. Arc lengthening is therebyaugmented, and an indication ofa blown fuse condition is obtained.Simultaneously with the withdrawing motion of the fuse-link flipper 108,there occurs unlatching of the cutout toggle mechanism 88. Preferably,arc extinction occurs within fuse tube 76 prior to breaking or collapseof toggle means 8S to prevent any arcing at the contacts.

The force exerted by the lower back-up spring 32 acts to break thetoggle means 8S and eifect counter-clockwise rotation of supporting link87 about its pivot axis 53, thus effecting outward and dropping movementof the fuseholder door 57 upon collapse of the toggle means 88. At thesame time, the upper contacts will exert a downward force on the Contact74 to assist in breaking the toggle 88. The tapered contact 74 will beurged downwardly away from the canted contact portions 156. Thefuse-holder 57 will swing in a counterclockwise direction about thepivot pins 53 to the dot-dash open position of FIG. 3.

While there has been shown and described a particular embodiment of theinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention, andthat it is intended by the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

We claim as our invention:

l. A fuse cutout comprising upper and lower stationary contacts spacedapart from one another, a tubular fuse holder having a contact formed atthe extreme end portion thereof disposed to engage said upper contact, afixed support pivot, a link member pivotally connecting said fuse holderto said xed support pivot and forming therewith a collapsible togglemeans, a fuse link carried by said fuse holder and normally cooperatingwith said fuse holder and said link member to prevent the collapse ofsaid toggle means, said upper stationary contact comprising a pair ofresilient Contact strip members extending outwardly from a common planeand having integral intermediate portions the integral intermediateportions of said Contact members being laterally spaced apart andgenerally curved to prevent lateral movement of one end of said fuseholder in either direction, said intermediate portions being flaredoutwardly in a direction toward said lower contact to apply an axialforce to said fuse holder in the latter direction to urge the contact ofsaid fuse holder out of engagement with said Contact members when saidfuse fuses, the shape of said Contact at the extreme end portion of saidfuse holder being tapered adapted to substantially mate with theintermediate portions of said contact members with a substantial portionof the contact on said fuse holder engaging said contact strip members.

2. A fuse cutout comprising upper and lower stationary contacts spacedapart from one another, a tubular fuse holder having a contact formed atthe extreme end portion thereof disposed to engage said upper contact, afixed support pivot, a link member pivotally connecting said fuse holderto said fixed support pivot and forming therewith a collapsible togglemeans, a fuse link carried by said fuse holder and normally cooperatingwith said fuse holder and said link member to prevent the collapse ofsaid toggle means, said upper stationary contact comprising a pair ofresilient contact strip members extending outwardly from a common planeand having integral intermediate portions, the integral intermediateportions of said contact members being laterally spaced apart andgenerally curved to prevent lateral movement ot one end of said fuseholder, said intermediate portions being flared outwardly in a directiontoward said lower contact to apply an axial force to said fuse holder inthe latter direction to urge the contact of said fuse holder out ofengagement with said contact members when said fuse fuses, the shape ofsaid contact at one end of said fuse holder being frusto-conical andadapted to substantially mate with the intermediate portions of saidcontact members when said fuse fuses, the shape of said contact at theextreme end portion of said fuse holder being tapered adapted tosubstantially mate with the intermediate portions of said conact memberswith a substantial portion of the contact on said fuse holder engagingsaid contact strip members.

3. A dropout fuse cutout, comprising: upper and lower ant/sees spacedapart line contacts; at least the upper contacts comprised of a pair oflaterally opposed contact members extending outwardly from a commonplaneand diverging downwardly; a fuse link including an upper Contact; afuse holder mounting said link for motion inwardly between said members;said fuse holder including means operable when released to permitmovement of said contact of said fuse link downwardly for efiectingrelease of the contact from said contact members, the extreme endportion of said fuse holder forming a Contact terminal; said contactmembers each being shaped to provide integral means thereon for latchingsaid contact terminal therebetween to prevent lateral movement of saidcontact terminal and being ared laterally outwardly and downwardly toapply a downward axial force to said fuse holder, said contact terminalof said fuse holder being tapered to fit in substantially matingrelationship between said upper contact members with a substantialportion of said contact terminal engaging said contact members.

4. A dropout fuse cutout, comprising: upper and lower spaced linecontacts; a fuse tube disposed to extend between said contacts, theextreme end portion of said fuse forming a contact terminal, a fuse linkdisposed in said fuse tube and having an upper Contact thereon; a pivotfixed with respect to said contacts; collapsible linkage connecting saidfuse tube to said pivot; said linkage forming a rigid link between saidtube and pivot when held in a first position; said linkage collapsibleto shorten the length between the tube and pivot; said fuse linkconnected to one of said contacts holding said linkage in said iirstposition and fusible to permit collapse of said linkage; said upper linecontacts comprising a pair of laterally opposed arms laterally curved toengage said contact terminal of said fuse tube and to prevent lateralmovement of said fuse tube and vertically diverging to apply a downwardforce to said fuse tube and to assist in etecting release of said fuselink contact when said linkage collapses, said contact terminal of saidfuse tube being tapered in shape to substantially mate with said pair ofopposed arms with a substantial portion of said contact terminalengaging said opposed arms.

5, A dropout fuse cutout, comprising: a pair of upper and lower spacedline contacts; at least the upper line contacts comprising a pair ofrelatively stationary laterally opposed contact members extendingoutwardly from a common plane, a movable member, said pair of contactmembers being adapted to engage one end of said movable member atopposite sides thereof when the movable member is moved inwardly betweenthe Contact members; said contact members including bent portionsintermediate the ends thereof for preventing lateral movement in eitherdirection of said movable member, said Contact members each extendingdownwardly in a relatively laterally diverging direction away from theother of said contact members to apply a downward axial force to saidmovable member; said movable member comprising a fuse holder means andfuse link means and having an upper contact formed thereon at theextreme end portion of said fuse holder means and being operable about apivot to move said upper Contact inwardly between said pair of contactmembers; said fuse holder means including a linkage collapsible to movesaid fuse link in a downward direction to eect release of said uppercontact from said pair of contact members; said fuse link means normallyholding said linkage in a non-collapsed position and fusible to permitcollapse of said linkage; said upper Contact having a taperedconiiguration substantially complementary to that of the divergingportions of said pair of Contact members with a substantial portion ofthe upper contact or" said fuse holder means engaging said Contactmembers.

References Cited by the Examiner UNITED STATES PATENTS 1,878,017 9/32Steinmayer 200-114 2,134,075 10/38 Dey 200-114 2,176,045 10/39Birkemaier 20G-114 2,260,751 10/41 Lincks 20G-114 2,335,062 11/4-3Hermann 200114 2,372,126 3/45 Schultz 200--114 2,525,999 10/50Birkemaier 20G-114 2,777,118 1/57 Sundt 20G-133 BERNARD A. GILHEANY,Primary Examiner'.

ROBERT K. SCHAEFER, Examiner.

3. A DROPOUT FUSE CUTOUT, COMPRISING: UPPER AND LOWER SPACED APART LINECONTACTS; AT LEAST THE UPPER CONTACTS COMPRISED OF A PAIR OF LATERALLYOPPOSED CONTACT MEMBERS EXTENDING OUTWARDLY FROM A COMMON PLANE ANDDIVERGING DOWNWARDLY; A FUSE LINK INCLUDING AN UPPER CONTACT; A FUSEHOLDER MOUNTING SAID LINK FOR MOTION INWARDLY BETWEEN SAID MEMBERS; SAIDFUSE HOLDER INCLUDING MEANS OPERABLE WHEN RELEASED TO PERMIT MOVEMENT OFSAID CONTACT OF SAID FUSE LINK DOWNWARDLY FOR EFFECTING RELEASE OF THECONTACT FROM SAID CONTACT MEMBERS, THE EXTREME END PORTION OF SAID FUSEHOLDER FORMING A CONTACT TERMINALS: SAID CONTACT MEMBERS EACH BEINGSHAPED TO PROVIDE INTE-